We don't have any plans to add more email providers in the near future. 

However, if you are looking to send follow up email campaigns, Judge.me has an integration with Zapier that triggers an event to Zapier when a review is created. You can enable it in our app setting here and set it up in Zapier https://zapier.com/developer/public-invite/22161/e9587c4d2e86cc29ca5b13313c49ca3a/

You can then use Zapier to set up subsequent flows with most email providers like Mailchimp and Omnisend, for example, send out a specific campaign to customers who leave good reviews to ask for reviews in other channels, send a thank you email, or ask for referrals.